Conventionally, the allocation of a frequency spectrum and the licensing to operators for mobile broad band (MBB) has been done in an exclusive manner, i.e. each operator obtains and licenses a fixed certain part of the frequency spectrum for exclusive usage. Such an exclusive frequency spectrum licensing and allocation has the advantages of a certain guarantee of quality of service (QoS), good interference management and a high degree of market certainty which was considered necessary to create adequate investment and innovation incentives. However, as the demand on mobile data traffic grows exponentially, the problem of “spectrum shortage” arises, i.e. there will be not enough spectrum bands or subcarriers, especially in the range below 6 Ghz, to be exclusively allocated and licensed to different operators. In other words, there is a need for more available frequency spectrum or a better usage of the currently available frequency spectrum. Even assumed that there is a sufficient amount of spectrum bands available in the available frequency spectrums for exclusive allocation, the mobile operators will face the pressure of a high spectrum cost. Such high costs for licensing and operation will become less and less acceptable. Furthermore, an exclusive allocation of frequency spectrum bands has the disadvantage of a low flexibility and low scalability, i.e. it often leads to an underutilization of the available resources in certain locations/regions and/or in certain periods of time. In other words, the efficiency of the usage of the available frequency spectrum is low. Thus, frequency spectrum sharing becomes a necessary and important tool to meet future spectrum requirements. On the one hand, mobile operators will have to share the available frequency spectrum with other communication or non-communication systems. On the other hand, mobile operators will have to share at least certain amounts, if not all, of the available frequency spectrum with each other. Actually, both sharing cases may occur simultaneously, for example, several operators may share a frequency band with a radar service in a primary/secondary manner, while they share the available frequency band with each other on an equal basis.
In the prior art, inter-operator spectrum sharing solutions normally work well only under ideal network deployment, e.g. all operators have collocated base stations, BSs, identical network deployment and homogenous Radio Access Network, RAN (same cell size everywhere). In practice, such ideal network deployment can only be found in delimited and special cases of RAN sharing. In a more general case, different operators have independent network deployments. Moreover, within the RAN of each operator, the cells would have various sizes and shapes in order to adapt to various network deployment environments or scenarios. For such realistic network deployment, the inter-operator spectrum sharing solutions of the prior art do not work well. Thus, a more efficient solution is required for realistic network deployment to allow a flexible spectrum sharing between operators.
In future wireless communication systems, a considerable part of the allocation of the available frequency spectrum will have to be done in a dynamic way and to sharing operators. This can for example be done under a licensed shared access, LSA, framework, where the frequency band of an incumbent user, for example a radar service, is temporarily licensed to multiple operators in a certain location and for a certain time period. Another example would be that the regulator licenses a spectrum band to multiple operators without fixed boundaries between the spectrum bands allocated to the different operators, so that the operators can coordinate their spectrum usage according to mutual agreement and/or specific or varying sharing rules. Irrespective of the scenario under which the spectrum is shared between operators, the key problem is the allocation of a certain available frequency spectrum band for shared usage to multiple, i.e. at least two operators. In an example of a previously suggested frequency spectrum sharing technique, Orthogonal Frequency-Division Multiplexing, OFDM, waveform is used, and fragments of the frequency spectrum, i.e. frequency subcarriers of the frequency spectrum, are allocated to the operators in an orthogonal manner. Orthogonal hereby and in the frame of the present application generally means that a specific subcarrier, or a specific group of subcarriers, or a frequency subband is only allocated to a specific operator, but not at the same time allocated to a different operator. At a given point of time, each frequency subcarrier or subband is therefore allocated to a specific operator, but not to two operators at the same time. The mutual interference between adjacent spectrum fragments consisting of subcarriers/subbands allocated to different operators can therefore be avoided by such orthogonal allocation of the resource blocks, i.e. subcarrier/subband fragments.
The present application and the technology underlying the invention, as later described, bases on partitioning of a shared frequency spectrum dynamically into frequency spectrum fragments and the allocation of the frequency spectrum fragments to the different operators. In order to minimize inter-operator or co-channel interference, different operators are allocated orthogonal sets of frequency spectrum fragments. The amount of allocated frequency spectrum for each operator should be adapted to the traffic demand of this operator, while taking the sharing policy into account, which is for example fairness or balance and so forth.
FIG. 1 shows an illustration for two cases in which the operators sharing the frequency spectrum have an ideal network deployment. Ideal network deployment is defined as a network deployment of different operators that is done in such a way that each sector or cell (in the shown example, each cell has 3 sectors of the same size) of one operator is only overlapping with only one sector or cell of another operator, respectively. A typical example is that cells of all operators have the same size and shape. FIG. 2 now shows two examples, an example 1 of non-co-located base stations 210, 220 and an example 2 of co-located base stations 210, 220. The base stations 210 belong to operator 1 (indicated by the solid lines of the cells around the base stations 210) and the base stations 220 belong to operator 2 (visualized by the broken lines of the cells around the respective base stations 220). In example 2, the base stations 210 and 220 are at the same location and the cells and sectors are co-located, i.e. are identically overlapping each other. In example 1, the base stations 210, 220 are non-co-located, but the respective sectors of each cell are identically co-located with respective sectors of an adjacent cell of the base station of the respectively different operator. Under such ideal network deployment and by ignoring inter-cell and inter-sector interference within each operator's network, each overlapping sector or cell contains the signals transmitted by one base station 210, 220 of each operator. Therefore, the spectrum partition pattern for each such overlapping sector or cell can be different and be handled independently. Here, the spectrum partition pattern is a pattern which defines the size and position of each frequency spectrum fragment as well as to which operator it is allocated. With each spectrum partition pattern, different operators are allocated orthogonal sets of spectrum fragments. Typically, the spectrum partition pattern of each such overlapping sector or cell is adapted to the traffic demand of each base station 210, 220 of each operator in a flexible manner.
In FIG. 2, an example of a realistic network deployment taking into consideration the co-channel interference is visualized. In a realistic implementation, the cells of the different base stations 210, 220 of the different operators have various and different sizes. Moreover, each sector or cell of one operator can be overlapping multiple sectors or cells of another operator. Under such realistic network deployment, if each sector or cell of one operator applies a different spectrum partition pattern, co-channel interference can occur, which means that in a certain overlapping area of the sectors or cells of different operators, a common spectrum fragment is used, causing inter-operator interference. Such co-channel interference is visualized in FIG. 2 by the fragment 2, which is used by both operators in an overlapping area of the sectors. Therefore, the user terminals using this fragment 2 in each of the overlapping sectors or cells can suffer from co-channel interference between operators.